This invention relates to a gas adsorbent including either a zeolitic adsorbent such as synthetic or natural zeolite or a silica-alumina adsorbent such as silica gel or alumina gel and also relates to a process for producing such a gas adsorbent.
Adsorbents in common use include synthetic and natural zeolites, activated carbon, and silica-alumina adsorbent which means silica gel, alumina gel or gel of their composite. These are employed singly as a mass or as a stack of multiple layers or a mixed bed of different adsorbents, depending on the intended use. Usually, individual adsorbents have limited applications; they do not singly serve all purposes but work only selectively and severally. Requirements of adsorbent performance for particular purposes are often not satisfied, and therefore various adsorbents possessing novel functions and capacities are needed. For example, removal by adsorption of nitrogen oxides (NO, NO.sub.2, etc.), sulfur oxides (SO.sub.x), and sulfur compounds (H.sub.2 S, organosulfur compounds, etc.) is involved in pollution control, exhaust gas treatment, prerefining for gas separation, and other operations. For these purposes adsorbents having optimum properties, i.e., high adsorptivities, are being called for. Synthetic zeolites, for example, exhibit excellent performance in separating and drying hydrocarbons and in removing carbon dioxide gas, but the very low rates of nitrogen oxide removal by adsorption have hampered their practical use. Aside from the synthetic zeolites, silica gel and alumina gel are known adsorbents ror nitrogen oxide removal. However, their removal rates have again been too low for practical purposes.